New nanoscale transistors allow sensitive probing inside cells

Aug 12, 2010

This is a to scale schematic of a kinked-nanowire electronic sensor probing the intracellular region of a cell. The two-terminal device has a three-dimensional and flexible structure with the key nanoscale transistor element synthetically-integrated at the tip of the acute-angle nanowire nanostructure. 3-D nanoprobes modified with phospholipid bilayers enter single cells in a minimally-invasive manner to allow robust recording of intracellular potential. Credit: Courtesy of Charles Lieber, Harvard University.

Chemists and engineers at Harvard University have fashioned nanowires into a new type of V-shaped transistor small enough to be used for sensitive probing of the interior of cells.

The new device, described this week in the journal Science, is smaller than many viruses and about one-hundredth the width of the probes now used to take cellular measurements, which can be nearly as large as the cells themselves. Its slenderness is a marked improvement over these bulkier probes, which can damage cells upon insertion, reducing the accuracy or reliability of any data gained.

"Our use of these nanoscale field-effect transistors, or nanoFETs, represents the first totally new approach to intracellular studies in decades, as well as the first measurement of the inside of a cell with a semiconductor device," says senior author Charles M. Lieber, the Mark Hyman, Jr. Professor of Chemistry at Harvard. "The nanoFETs are the first new electrical measurement tool for intracellular studies since the 1960s, during which time electronics have advanced considerably."

This shows the delivery of a two-terminal nanoscale transistor sensor into single cells. The device has a three-dimensional and flexible structure with the key nanoscale field-effect transistor element synthetically-integrated at the tip of the acute-angle nanowire nanostructure. 3-D nanoprobes modified with phospholipid bilayers enter single cells in a minimally-invasive manner to allow robust recording of intracellular potential. Credit: Courtesy of Charles Lieber, Harvard University.

Lieber and colleagues say nanoFETs could be used to measure ion flux or electrical signals in cells, particularly neurons. The devices could also be fitted with receptors or ligands to probe for the presence of individual biochemicals within a cell.

Human cells can range in size from about 10 microns (millionths of a meter) for nerve cells to 50 microns for cardiac cells. While current probes measure up to 5 microns in diameter, nanoFETs are several orders of magnitude smaller: less than 50 nanometers (billionths of a meter) in total size, with the nanowire probe itself measuring just 15 nanometers in diameter.

This is an optical image of a two-terminal nanowire nanoprobe internalized by a single cell. The device has a three-dimensional and flexible structure with the key nanoscale field-effect transistor element synthetically-integrated at the tip of the acute-angle nanowire nanostructure. 3-D nanoprobes modified with phospholipid bilayers enter single cells in a minimally-invasive manner to allow robust recording of intracellular potential. Credit: Courtesy of Charles Lieber, Harvard University

Aside from their small size, two features allow for easy insertion of nanoFETs into cells. First, Lieber and colleagues found that by coating the structures with a phospholipid bilayer - the same material cell membranes are made of - the devices are easily pulled into a cell via membrane fusion, a process related to that used to engulf viruses and bacteria.

"This eliminates the need to push the nanoFETs into a cell, since they are essentially fused with the cell membrane by the cell's own machinery," Lieber says. "This also means insertion of nanoFETs is not nearly as traumatic to the cell as current electrical probes. We found that nanoFETs can be inserted and removed from a cell multiple times without any discernible damage to the cell. We can even use them to measure continu-ously as the device enters and exits the cell."

Secondly, the current paper builds upon previous work by Lieber's group to introduce triangular "stereocenters" - essentially, fixed 120º joints - into nanowires, structures that had previously been rigidly linear. These stereocenters, analogous to the chemical hubs found in many complex organic molecules, introduce kinks into 1-D nanostructures, transforming them into more complex forms.

Lieber and his co-authors found that introducing two 120º angles into a nanowire in the proper cis orientation creates a single V-shaped 60º angle, perfect for a two-pronged nanoFET with a sensor at the tip of the V. The two arms can then be connected to wires to create a current through the nanoscale transistor.

Related Stories

(PhysOrg.com) -- Taking nanomaterials to a new level of structural complexity, scientists have determined how to introduce kinks into arrow-straight nanowires, transforming them into zigzagging two- and three-dimensional ...

Findings could point the way to ultra-powerful new diagnostic tools and bioterror detectors
Harvard University scientists have found that ultra-thin silicon wires can be used to electrically detect the presence of single viruses, in real time, with near-p ...

You may not have noticed, but the smallest revolution in world history is under way. Laboratories and factories have begun to make medical sensors and computer-chip components smaller than a single blood cell ...

(PhysOrg.com) -- Engineering researchers at the University of Arkansas have developed a neural probe that demonstrates significantly greater electrical charge storage capacity than all other neural prosthetic ...

Nowadays, a myriad of silicon transistors are responsible to pass on the information on a microchip. The transistors are arranged in a planar array, i.e. lying flat next to each other, and have shrunk down ...

Recommended for you

Thanks to the work of an interdisciplinary team of researchers at the Dartmouth Center of Nanotechnology Excellence, funded by the National Institutes of Health, the next-generation magnetic nanoparticles ...

Here's the rub with friction—scientists don't really know how it works. Sure, humans have been harnessing the power of friction since rubbing two sticks together to build the first fire, but the physics of friction remains ...

Physicists at the University of Basel have shown for the first time that electrons in graphene can be moved along a predefined path. This movement occurs entirely without loss and could provide a basis for ...

Solar cells made out of lead sulfide quantum dots could eventually offer a cheaper, more flexible alternative to ones made using silicon, but they are currently much less efficient. However, altering the ...

Chemotherapy often shrinks tumors at first, but as cancer cells become resistant to drug treatment, tumors can grow back. A new nanodevice developed by MIT researchers can help overcome that by first blocking ...

Lithium-sulfur batteries have been a hot topic in battery research because of their ability to produce up to 10 times more energy than conventional batteries, which means they hold great promise for applications ...

User comments : 1

This is interesting work. However, it is not the first intracellular recording using a semiconductor-based device. The first recording using a semiconductor-based multi-electrode array was published on Nature Methods, 2010, 7(3):200-202.

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.

Javascript is currently disabled in your web browser. For full site functionality, it is necessary to enable Javascript.
In order to enable it, please see these instructions.